Provenance — where it came from
In the 2000s, Japanese music fans borrowed the English word “emo” for a genre of confessional rock. For a while, エモい (emo-i) was insider talk: music that sounded like emo.
In the mid-2010s the word escaped music, and its meaning widened into something English cannot say in one word. Emo-i is a sunset over power lines. An old photograph. The smell of a summer evening that reminds you of a summer you cannot place. It means: this moves me, in a way that is somehow nostalgic and somehow sad, and I do not have a better word for it. That last part is the point — emo-i exists precisely for feelings that have no exact name.
The recipe is worth noting: an English word, plus い, the ending of a Japanese adjective. It has appeared before — exhibit № 001, ナウい, built the same way from “now.” Nau-i lasted roughly one decade. How emo-i will age is not yet known.
Field notes — how it’s used
夕暮れの商店街、エモかった
yūgure no shōtengai, emokatta
“The shopping street at dusk — it was emo-i.” Past tense, like any native adjective.